The incidence rate of both benign and malignant primary central nervous system (CNS) tumors is 18.16 per 100,000 person-years in the general population. The incidence of primary CNS tumors is highest among those 75 to 84 years old (63.75 per 100,000 person-years). In addition, as the elderly segment of the general population grows faster than any other age group, the number of primary brain tumors in older adults is expected to increase. Certain tumor histologies are especially common in older adults;for example, the incidence of glioblastomas, anaplastic astrocytomas, and primary CNS lymphoma (PCNSL) peaks in the seventh decade, and the incidence of meningiomas rises steadily with age. Several factors make the treatment of CNS tumors in the elderly unique. Poor overall health status, the presence of multiple comorbidities, and polypharmacy may pose a significant challenge in managing older patients with brain tumors. In addition, advanced age is a well-known prognostic factor associated with worse survival when adjusted for histologic diagnosis and tumor grade. Finally, elderly patients are underrepresented in clinical trials because of study-imposed restrictions, coexisting conditions, concern about the toxic effects of treatment, or the reluctance of physicians to enroll elderly patients in these trials. Our project objectives are: 1) to devise better ways to assess prognosis in patients with glioblastomas;2) to evaluate patterns of care of elderly patients with CNS tumors in the SEER-Medicare database;3) to evaluate underlying molecular and neuroimaging differences between younger and older patients with gliomas (in collaboration with Howard Fine's group).